PDF security overview
There are two types of secured PDF documents: your file can ask for password when
opening the document, or, your file opens normally, but some operations are
restricted (e.g, printing or editing) and requires password for unlocking it.
The first password is known as document open (or user) password, and the second
is permissions password (also known as a master or owner
password). Adobe Acrobat uses different algorithms to apply PDF security with 40, 128 and 256 bit keys.

PDF restrictions are insecure and permissions password could be removed instantly.

If open password uses 40-bit keys (Acrobat 3 compatible encryption), it also could be removed with guarantee.

remove restrictions (unlock) of any secure PDF document
(you should have the right to do it, for example,
if you forgot the password). Any Acrobat version up to X is supported, even with 256-bit AES or
128-bit RC4 encryption. PDF restrictions removal is an instant process. Unlocked
file can be opened in any PDF viewer without any restrictions so you may
edit, copy or print it.

GuaPDF can be also used for

remove PDF open password (a.k.a. user password).
Decryption of the file with password for opening is guaranteed for PDF
documents with 40-bit key only. This process takes 1-2 days on one modern desktop computer and could be accelerated on GPU.

Unlike most PDF password crackers, your PDF file is not altered in any way (except the decryption), even the file size
is often the same. That minimizes the possible incompatibility of
the unlocked PDF file.

GuaPDF is the first and unique software with GPU acceleration of user
password removal.

DEMO (freeware) version. It demonstrates processing of both security methods but has some limitations and can correctly decrypt only small files. It also doesn't contain distributed computing mechanism.

GuaPDF restriction remover.
This version can remove restrictions on PDF files (remove permissions passwords), and can't decrypt files with open password.
(from $/€25)

GuaPDF password remover.
This version process both security methods (i.e. open and
permissions passwords), and supports up to Quad-core CPU and/or one GPU card for fast 40-bit key
searching. (from $/€39)

All these version are licensed for non-commercial purposes only. If you wish to use GuaPDF to make any profit you should use

Distributed UNLIMITED, most powerful version. It does everything, has no limitations, support any number of CPU/GPU clients and distributed processing ($/€150)

Order the commercial versions over the Internet worldwide using secure connection. This means no one (including us)
can intercept your confidential information. The temporarily link to the fully functional version you
receive immediately after verifying your order. Normally you'll get the program within 10-15 minutes.

A: GPU acceleration is used only if your file has password to open with 40-bit key.
Also, you need modern NVIDIA (from 8000 series) or AMD/ATI Radeon (from 5000 serie) and the latest
OpenCL
drivers.
Under Mac OS X 10.6 (Snow Leopard) you may need to boot in 32-bit mode.

Q: What version should I choose?

A: If can open PDF file, but can not print, edit etc, get the restriction remover version.
If you can't even open file, first of all you need to test your file (using DEMO version) if it has 40-bit key encryption.
If yes, you may choose any version depending of number of computers you've got.

A: DEMO version can process small files only. In fact, unlike other PDF decrypion
software, GuaPDF don't change anything in your file structure, it only decrypts all
encrypted streams and strings. That's why the decryption is guaranteed: your file is not
modified (even the file size is often the same after decryption). DEMO version has
only one possible limitation: it decrypts only few streams, all others streams remain
encrypted. So, if the large files contains more streams than DEMO limitation, the decryption may cause
any errors and blanks (non-decrypted) pages.

Q: Ok, but how can I sure the full version will work on my file?

A: If DEMO version parses your file with no errors and the key is printed, the full version will
work fine, because the decryption with known key is trivial.

Q: Ok, how long will it take?

A: Restriction removal is instant (may be few minutes on very large files). To estimate key searching time, run DEMO version (and divide it to the number of your PCs/CPU cores).

Q: Are non-standard security handlers supported?

A: No, please run DEMO to make sure your file is supported.

More questions and answers you'll find in the included documentation and here.

Only legal customers are supported. No claims and question about freeware version will be accepted, but I'll appreciate the constructive feedback. Also contact me if you have any problems with ordering the program.